Following months of speculation, a live BBC1 programme has unveiled the Thick of It star as the latest incarnation of the Time Lord

After months of feverish speculation, the actor, best known to viewers as the star of The Thick of It, was unveiled as Matt Smith’s replacement during a live BBC1 programme this evening.

"It's so wonderful not to keep this secret any longer!" the self-confessed "lifelong Doctor Who fan" told the studio audience (and viewers at home).

"You look in the mirror and suddenly, strangely, [the Doctor] is looking back. And he’s not me yet but he’s reaching out. And hopefully we’ll get it together..."

In a recorded interview prior to the big reveal, Smith said of his sucessor "If I was gonna pick someone... I'd pick him...

"If I had to give him a message, I'd say 'You're gonna have to work hard, buddy'.

"I'm excited because I know what's coming and he's gonna have a blast."

On leaving the role, Smith added: "It's the greatest year in show's history and I'm passing it on to the next with a smile... It's been great, man. It's a really cool job. It'll be hard to top."

The incumbent Time Lord was among the guests on tonight’s show – Doctor Who Live: The Twelfth Doctor – who also included fifth Doctor Peter Davison, fellow Who alumnus Bernard Cribbins and celebrity fans Daniel Roache, Rufus Hound and Liza Tarbuck.

There were contributions, too, from Sixth Doctor Colin Baker, and former companions Anneke Wills, who played Polly, Katy Manning, aka Jo Grant, Janet Fielding, who was Tegan, and Bonnie Langford, known to fans as Mel.

Smith, who has played the Doctor for four years announced in June that he is to leave the role at the end of the year. He will bow out – regenerating into Capaldi’s twelfth Doctor – at the end of the Christmas special, after starring in the much anticipated 50th anniversary special on 23 November.